Non-woven fabric

ABSTRACT

A NON-WOVEN FABRIC COMPRISING A FIBROUS MAT BOUNDED WITH COLLAGEN, THE CONCENTRATION OF COLLAGEN DECREASING FROM THESURFACE INWARDLY. IN THIS WAY, THE HIGH-COLLAGEN SURFACE CAN BE APPLIED AGAINST WOUNDS, WITH WHICH IT IS CHEMICALLY COMPATIBLE. BY COATING THE LOW-COLLAGEN SURFACE WITH PLASTIC SUCH AS POLYVINYLIDENE CHLORIDE AND FORMING A TUBE WITH THE HIGH-COLLAGEN SURFACE INSIDE, THE TUBE WILL CONFORM CLOSELY TO SAUSAGE MATERIAL FILLING EVEN IF THE LATTER SHRINKS, SO AS TO MAINTAIN A PLEASING APPEARANCE, THE PLASTIC EXTERIOR, HOWEVER, KEEPS THE PRODUCT IMPERVIOUS TO WATER VAPOR AND AIR.

3,728,207 NON-WOVEN FABRIC Wilhelm Heling, Benshein-Auerback, Germany, assignor to Carl Freudenberg, Postfach, Germany N Drawing. Filed Nov. 12, 1970, Ser. No. 89,043 Claims priority, application Germany, Dec. 12, 1969, P 19 62 331.5 Int. Cl. B321) /14 US. Cl. 161-151 2 Claims ABSTRACT OF THE DISCLOSURE A non-woven fabric comprising a fibrous mat bonded with collagen, the concentration of collagen decreasing from the surface inwardly. In this way, the high-collagen surface can be applied against wounds, with which it is chemically compatible. By coating the low-collagen surface with plastic such as polyvinylidene chloride and forming a tube with the high-collagen surface inside, the tube will conform closely to sausage material filling even if the latter shrinks, so as to maintain a pleasing appearance; the plastic exterior, however, keeps the product impervious to water vapor and air.

The present invention relates to bonded non-woven fabrics especially suited for wound dressings, sausage casings, and the like.

A bandage for a wound should fulfill the following requirements:

(1) It must not irritate the wound;

(2) It must be highly absorbent;

(3) It must be strong;

(4) It must not adhere to the wound through incrustation;

(5) It must permit the diffusion of heat.

The materials used today for the bandaging of wounds are almost exclusively textiles but the textile bandages and banding materials that have been commonly used hitherto satisfy these requirements only in part.

In addition, the bonding of non-woven fabrics with a collagen slurry is already known. For this purpose a loose fiber mat is impregnated with the collagen fiber slurry, dried, and subjected to an aftertreatment. The end product can be fabricated as synthetic leather. Processes for this purpose are described in the Journal of the American Leather Chemists Association, vol. LXIII, No. 1, January 1968, and in US. Pats. 3,063,892, 3,071,483, 3,073,714, 3,223,551, 3,269,851, 3,285,775, 3,294,579, and 3,294,581 and Canadian Pat. 749,911.

It is accordingly an object of the invention to provide a collagen bonded non-woven fabric which is especially suited for a variety of end uses including surgical dressings, pads, casings for sausages, and the like.

This and other objects and advantages are realized in accordance with the present invention wherein a fibrous mat is bonded with collagen, the concentration of the collagen decreasing from a maximum value adjacent one surface. The concentration may reach a minimum at the other surface or in the interior of the mat, increasing again toward the other surface. This is in contrast with the prior art non-Wovens wherein every effort was made to distribute the collagen binder uniformly throughout.

It has been found that the higher the collagen content in the bandage, the more gentle is its effect on the wound. Probably this is due to the fact that the collagen and the edges of the wound have the same chemical structure and are thus compatible.

To manufacture the non-woven fabric of the invention, a fiber mixture of, for example, equal parts of staple rayon fiber and wood pulp, is suspended in a great excess of water. At the same time the water contains collagen United States Patent 0 "ice fiber slurry. This mixture is then floated onto a slanting screen. A fiber mat mixture is then left on the screen and contains from about 5 to 10% collagen, depending on the amount of collagen used. At the upper end of the slanting screen there is another tank containing a collagen dispersion. This dispersion is then allowed to run into the screen below it, the collagen concentrating at the surface of the already collagen-doped mat. The excess water is removed by vacuum in the usual manner.

Then the wet mat is dried by passing it through a drying chamber or over a drying cylinder, whereupon the material solidifies.

Then the collagen present in the mat must be tanned. This is performed most simply by spraying the collagenhardened fiber mat with an aqueous solution containing aldehydes, preferably glutaric aldehyde. The aldehyde then tans the collagen.

According to one embodiment of the invention, small amounts of a thermoplastic powder, such as polyvinyl acetate, for example, are added to the suspension of the textile and collagen fibers in an excess of water (up to 10% of the total weight of the final product). This has the advantage that the end product can be bonded to gether by heat along certain lines.

This offers a very simple way of producing surgical pads. In making these pads, two layers of the material of the invention are used, which contain thermoplastic powder, and they are laid one on the other so that the surfaces that are low in collagen are in contact. Between the two layers there is then placed another layer of highly absorbent plain fibers. This three-layer assembly can then be welded at the edges by the high-frequency or heat pulse method, whereby the thermoplastic powder present in the two outer layers softens, resulting in a strong bonding together of all three layers. If a square-shaped sandwich is welded at the margins, a so-called surgical pad is obtained which is gentle to wounds on account of the high collagen content, and which, due to the absorbent material inserted between the covers, is also capable of absorbing large amounts of the secretions from the wound.

In place of thermoplastic powder as binder, thermoplastic fibers can be included in the mix from which the initial non-woven mat is prepared. As noted, heat sealing or activation can be effected peripherally to form a pad with the absorbent fibrous layer completely enclosed or it may be made along predetermined lines, continuous or discontinuous, the bond extending through the fibrous layer to secure it to both outer fabrics.

Particularly good results are obtained by adding polypropylene fibers to the outer layers instead of viscose fibers, since they are thermoplastics and are not wetted by aqueous liquids. However, any fibers, natural or synthetic, may be used, e.g. nylon, silk waste, polyester, acrylics, polyethylene, acetate, cotton, and the like. The fibers may be present in short staple form or in substantially continuously lengths. The deniers may be any of those normally encountered, e.g. as little as about 1 up to about 50 or more, although advantageously the denier ranges from about 2 to 25 and preferably about 2 to 15.

The material of the invention, however, can also be used for other applications. For example, if the lowcollagen side is coated with a film of plastic such as polyvinylidene chloride, this material is suitable for the packing of sausage meat and for use as artificial casing. The high-collagen side can both swell and shrink, thereby assuring tight contact with the stuffing. On the other hand, the polyvinylidene chloride adheres very well to the lowcollagen side. If it should be applied to the high-collagen side it would come loose from it.

Polyvinylidene chloride is completely impervious to water vapor and air, which is essential for many applications. Sausage meat can also be packed in plain sheet polyvinylidene chloride, but if this material is used to make an artificial casing, it will adhere very poorly to the stuffing, and wrinkles and creases form detracting from the appearance of the product.

If, however, a polyvinylidene chloride film is combined with a collagen-bonded non-woven fabric having a high collagen concentration on one side, the casings will always lie tight and flat against the meat after the sausage stuffing operation.

Other plastic films may be similarly applied and employed and may form secure bonds with the underlying mat as a result of their affinity for the fibers thereof which are more accessible at the low collagen surfaces.

If the collagen-bonded non-woven fabric is conceived of as being made up of many superposed layers, the concentration of collagen in the uppermost layer may range from about 10 to 100% and in the lowermost layer may range from about 0.5 to 10% with the difference in collagen content from maximum to minimum value being at least about 1%, and preferably at least about 4%. The fabric can be conceived of as comprising only two layers, i.e. two levels of collagen concentration or it may comprise an infinite number of layers, i.e. the collagen concentration may range continuously from its maximum to minimum concentrations. The invention will now be described more fully in the following illustrative examples, wherein all parts are by weight unless otherwise expressed.

EXAMPLE 1 500 grams of a 50:50 mix of 3 denier 2 inch nylon-66 staple and 2 denier 3 inch polypropylene staple are suspended in 10 liters of water having 50 grams of collagen suspended therein, with agitation. The mix is filtered through a screen and after about half the suspension is deposited an additional 5 liters of water having 25 grams of collagen suspended therein is poured into the initial suspension at the same rate it is being filtered off. As a result there is formed a non-woven fleece having a collagen content from one of its surfaces to the middle and an in creasing content from 10% up to about 30% at the other surface. The product is tanned by contact with glutaric aldehyde at C., followed by drying. The fabric weighs 80 grams per square meter.

EXAMPLE 2 distributed throughout the fabric. Between the low-collagen surfaces of two such fabrics there are deposited loose cotton fibers weighing '60 grams per square meter and heat is applied along the edges of a three inch square to produce bonding. By cutting just outside the bond line a highly absorbent surgical pad is formed.

EXAMPLE 3 The fabric of Example 1 is coated on its low-collagen surface with a 5% solution of polyvinylidene chloride in carbon tetrachloride in amount sufficient to deposit 40 grams of polyvinylidene chloride per square meter, the solvent thereafter being evaporated. By stitching longitudinally with the polyvinylidene on the outside there is formed a tubular casing which, when filled with sausage, keeps the sausage from drying out; the casing adheres snugly to the filling.

It will be appreciated that the instant specification and examples are set forth by way of illustration and not limitation and that various modifications and changes may be made without departing from the spirit and scope of the present invention.

What is claimed is:

1. A non-woven fabric comprising a fibrous mat, collagen binding the fibers of said mat together, the concentration of collagen being higher at one of the fabric surfaces than at the other surface, and a plastic film coating the lower collagen other surface, whereby when used to wrap meat with the high collagen surface in contact with such meat said fabrc will adhere snugly to the meat even upon shrinkage of the meat.

2. A non-woven fabric according to claim 1, wherein said plastic film comprises polyvinylidene chloride.

References Cited UNITED STATES PATENTS 3,223,551 12/1965 Tu 117-140 R 3,208,875 9/1965 Holden 117-1355 3,440,131 4/1969 Tu 16159 3,362,849 1/1968 Tu 1l7-l'40 R 3,294,579 12/1966 Tu 117140 3,285,775 11/1966 Tu ll7140 2,202,566 5/1940 Schulte 128Collagen Digest 3,276,448 10/1966 Hronenthal 128334 3,272,204 10/1966 Artandi et al. 128-155 3,366,440 1/1968 Nuwayser 8127.5

WILLIAM A. POWELL, Primary Examiner J. J. BELL, Assistant Examiner US. Cl. X.R. 

